Many working mothers end up leaving their jobs because they are sidelined in their work after having a baby, or feel they have to suppress their role as a mother, a research paper has suggested.

According to the UK paper, middle-class working mothers in professional and managerial jobs are often expected to start early, finish late and socialise outside of working hours, even if they have negotiated fewer working hours to take into account their childcare responsibilities.

The paper said that this is expected of them because the culture of work is still largely organised by men and they tend to be less involved in childcare.

"Unless mothers mimic successful men, they do not look the part for success in organisations," noted the paper's co-author, Emma Cahusac, a producer with the BBC and an organisational psychologist specialising in problems faced by organisations.

The paper noted that before they have children, many women accept, and even encourage, this work culture. However, when they became mothers, they find it difficult to combine work with their home life.

One women interviewed for the paper - Susan, an ex-banker - said that she started work by 8am every day and left work at 6pm. During this time, she ‘could do the job perfectly well', but one fellow female worker who did not have children used to make ‘barbed comments' every day when she left at 6pm.

Many of the women interviewed for the paper said that they felt they had to hide the fact that they had children.

"The male partners never talked about their families. They've been very adept at keeping that separation between work and home," noted Nadia, a lawyer.

Meanwhile others stated that they could never admit that they were taking time off to look after sick children.

"You definitely would have to say you were sick, not the kid was sick," commented one mother who held a senior position at a charity.

The research paper was based on interviews with 26 mothers who had given up their jobs either when they were pregnant, or after their return to work.

Twenty-one of the women chose to quit their jobs voluntarily, with many admitting this was because they were sidelined after returning to work.

"Many women leave high-powered jobs because they are relegated to lesser roles and feel the need to suppress their identities as mothers. This is not only unfair. As an economy, we cannot afford to waste such skilled and educated workers," said co-author, Shireen Kanji, of the University of Leicester School of Management.

Details of this paper are published in the journal, Gender, Work & Organization.